The production of leaded electrical components such as low pin-count Integrated Circuit (IC) components, for example the SOT23 (Small Outline Transistor for SOT), at very high speeds usually involves the use of rotary-indexed machines. Each IC component usually has three to six leads distributed on two of its opposing sides. During production, such IC components are held by their top surfaces by a pickup head on the rotary-indexed machines using vacuum suction. Each IC component is then indexed through different stations for different processes such as trimming, forming, electrical testing, marking and inspection processes. After processing, the IC components are transferred to a taping station where the IC components are adhered to a tape; this is known as the taping process. The tape is subsequently wound onto a reel for bulk packaging. For process and quality control purposes, the geometry of these IC components is usually inspected during their production.
In conventional ways of inspecting low pin-count IC components using rotary-indexed machines at very high speeds, implied measurement methods are typically involved. Such methods include the acquisition and analysis of a single view on the IC component. The acquisition of this single view is done with a camera that captures an image of the top of an IC component at the taping station. This type of top-view implied measurement method is used to infer defects such as bent leads from the length of the leads. The implied measurement method, however, is insensitive and thus gives inaccurate results when used. This implied measurement method is only effective in detecting leads on IC components that are distorted to a significant degree. On the other hand, if strict tolerance is imposed on the implied measurement method, a very high and impractical rejection rate will be obtained.
Other new and innovative solutions have also been proposed, one of which involves the capture of two orthogonal views of an IC component in a single image for analysis. The first view comprises the side view of the IC component, which may be effectively analyzed to provide curled leads and other types of information. The second view is orthogonal to the first view, and usually comprises the bottom view of the IC component. This second view enables lead length, pitch, width, terminal dimension and other types of information regarding the IC component to be determined.
Although the exemplified proposed solution allows the complete geometry of low pin-count IC components to be inspected, it has disadvantages. In this proposed solution, the first and the second views are provided by light that is reflected from the relevant surfaces on the IC components. Hence the quality of the captured image is subject to variations of the lead surface, the IC component package surface, and ambient light. The accuracy and reliability of the results may thus be compromised. Moreover, the lighting setup that provides the light must be changed when the type of IC component under inspection is changed. For example, the lighting setup needs to be tweaked in terms of direction or intensity when a three-lead IC component is changed to a five-lead IC component. Most importantly, however, the coplanarity of the IC component and the standoff of each lead on the IC component cannot be determined using this proposed solution.
Thus, a need exists for an IC component inspection system to measure the coplanarity of the IC component and provide standoff information for each lead on the IC component at very high speeds. The IC component inspection system should also test different types of IC components, each having a different pin-count, without any lighting adjustments.